Pressure relief valve arrangement for double acting hydraulic cushion



July 29, 1969 THOMPSON 3,458,054

PRESSURE RELIEF VALVE ARRANGEMENT FOR DOUBLE ACTING HYDRAULIC CUSHION Filed Jan. 15, 1968 @v NW mu MK k6 7} 1 0622101 .Z. YKomfnson 1 Wad Q km mm United States Patent US. Cl. 213-43 1 Claim ABSTRACT OF THE DISCLOSURE A pressure relief valve arrangement for a double acting hydraulic cushion device relieving buff and draft impacts imposed on the couplers of a railway car. The cushion device comprises a piston and rod assembly dividing a hydraulic cylinder into two chambers between which hydraulic fluid will flow through the provision of metering passages. The pressure relief arrangement comprises a valve orifice contained in the piston head and opening into one of the chambers. A pressure relief arrangement includes a valve member which is slidably positioned in a bore of the piston rod, said bore communicating with a passage which transmits hydraulic fluid to an accumulator chamber. The valve member is provided with a forward face adjacent to the orifice which is of frusto-conical structure and includes a plurality of passages extending obliquely in converging relation to an area provided on the rear face of the valve member. A coil spring contained in the bore urges the valve member and a spherical sealing element into closed relation with respect to the orifice. The coil spring has an inner diameter which is greater than the diameter of the area of convergence of the oblique openings so that during a predetermined pressure within one chamber fluid can flow in an uninterrupted manner through the annular spaces provided by the inner edges of the coils of the spring to the passage and therethrough to the accumulator chamber.

Cross reference to related application The present application is related in subject matter to the pending application of William H. Peterson entitled Double Acting Hydraulic Cushion, Ser. No. 658,782 filed Aug. 7, 1967.

Background of the invention The present invention relates to double acting hydraulic cushion units employed in railway cars for relieving the buff and draft impacts imposed on the couplers to thereby reduce both car and lading damage. Such double acting cushions are known as end-of-car cushions and are usually mounted in the draft sill ends of the car and associated with the couplers so as to be operative upon impact to the latter. The hydraulic cushions are normal ly constructed so as to be operative in both buff and draft so as to be capable of relieving both the buff and draft impacts. In cushions of this type it is particularly important that an eflicient pressure relief means is provided, which upon an overspeed impact, is effective to relieve the pressure during the buff stroke to prevent the destruction of the cushioning unit.

Description of the prior art The prior art is disclosed in the patents of Edwards et al. 2,816,670, Blake 3,207,324 and Peterson, 3,275,164. These patents disclose pressure relief devices for end-0fcar cushions and the present invention is an improvement thereover.

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Summary The invention is concerned with a pressure relief device for a hydraulic cushion assembly having a cylinder separated into two concentric chambers by means of a sliding piston which is connected to a rod in turn associated with the coupler of the draft gear. The piston is movable upon a buff impact through the first chamber whereupon fluid is metered around the piston to the second chamber. In the event of a draft impact the reverse operation occurs and thus a double acting unit is provided. Since impacts in buff may be excessive and greater than the unit has capacity for, an improved pressure relief valve mechanism is provided. Essentially the mechanism consists of a restrictive orifice provided in the head of the piston facing the first chamber the said orifice being normally closed by means of a frusto-conical valve member biased in a closed position by means of a coil spring. The valve member is provided with a pair of passages that extend from the front face thereof in oblique relation and converge in an area at the rear face of the valve member. The coil spring has an inner diameter substantially greater than the diameter of the area of convergence of said passages thereby effecting a rapid uninterrupted flow of fluid to a reservoir during an overspeed impact.

Brief description of the drawings FIG. 1 is a cross sectional view of a double acting hydraulic cushion unit embodying the principles of the present invention and showing the cushion unit in operative connection with a draft gear; and

FIG. 2 is a fragmentary perspective view in section showing details of structure of the cushion including a pressure relief valve mechanism therefor.

Description of the preferred embodiment Referring now to the drawings, there is shown a double acting hydraulic cushion unit 10 associated with a draft gear 11 to which there is connected at coupler (not shown). The cushion unit 10 comprises generally a cylinder 12 having fixed to one end thereof a base plate 14. Disposed intermediate the ends of the cylinder is an intermediate cylinder head assembly 16 which defines with the base plate 14 the limit of the travel of a piston assembly 17. The piston assembly 17 includes a piston head 18 and a piston rod 19 extending from one face thereof. The piston rod 19 extends through a stationary stop plate 20 and is connected at its outer end to a lengthwise movable plate 21 of the draft gear 11 so as to be responsive to movement of the coupler upon impact thereto in either buff or draft. As shown in FIG. 1, the piston head assembly 17 is shown in its normal neutral position so that upon the imposition of a buff impact the piston assembly moves to the left relative to the cylinder head assembly 16.

Connected between the intermediate cylinder head assembly 16 and the piston rod 19 is an accumulator chamber 22 which is in the form of a flexible boot. The flexible boot or chamber 22 serves to close off the open end of the cylinder 12 so that the latter may be charged with a hydraulic fluid. Formed in the piston head assembly is a fluid passage system 23 which provides communication between a first chamber 24 and (defined between the outboard face 25 of the piston head 18), a second chamber 27 (defined between the inboard face of the piston head 26 and the intermediate cylinder head assembly 16), and the accumulator chamber 22.

Disposed in the piston head end of the passageway system 23 is a relief valve assembly 28 which is operative during buff impact and upon a predetermined pressure within the first chamber 24 permits direct fluid com- 3 munication between said chamber 24, the second chamber 27 and the boot 22.

Mounted on the piston head assembly 18 is a slide valve assembly 29 which is operative to open communication from the chamber 27 to the fluid passage system 23 during movement of the piston head assembly 17 to the (left) buff position and to close off communication when the piston head assembly 17 moves in the opposite direction. When communication is open to the fluid passageway system 23, the hydraulic fluid displaced by the piston 18 in the chamber 24 to the chamber 27 is free to flow into the accumulator boot 22.

Formed on the inner wall of the cylinder 12 are a plurality of angularly spaced metering grooves 31 which are tapered in a manner such that upon movement of the piston head assembly 17 the cylinder hydraulic fluid is displaced at a metered rate between the chambers 24 and 27 so as to impart a predetermined force travel characteristic to the cushion unit and to achieve optimum car body and lading protection.

To obtain a predetermined cushion characteristic upon draft impact as the piston head assembly 18 moves relative to the cylinder to the neutral position after bufl impact, there is disposed in the intermediate cylinder head assembly 16 a flap valve 32 which closes off an annular passage 33 providing communication between the chamber 27 and the boot 22, as more fully to be explained hereinafter. When the cushion unit 10 returns to its neutral position the flap valve 32 moves away from the annular opening to permit a free flow of hydraulic fluid from the boot 22 to the chamber 27 so that the unit is again in condition to receive a buff impact. Disposed between the base plate 14 and the stationary plate is a return spring 34 which serves to return the piston head assembly to its neutral position in the event a draft force is not applied on the coupler.

More specifically, the cylinder may be formed of a tube or the like which is preferably formed with a preformed bore. The base plate 14 which may be of any suitable contour is provided with a peripheral groove into which one end of the cylinder is inserted and welded therein. It is to be observed that the base plate 14 projects from the outer periphery of the cylinder 12 so as to provide a ledge 36 which is engaged by one end of the return spring 34.

The intermediate cylinder head assembly 16 includes an annular disk 37 providing the axial opening 33 of somewhat larger diameter than the diameter of the piston rod 19 so as to define therein the annular opening 33. The annular disk 37 is held in fixed position against longitudinal movement by a collar 38 which abuts along one edge against a ledge 43 formed in the bore of the cylinder 12. On the other side of the disk 37 there is a clamp ring 39 which is held fixed by means of a snap ring 41.

The clamp ring 39 is formed on its inner face with a surface which is spaced from a boss 42 so as to clampably accommodate therebetween one beaded end 43 of the accumulator boot 22. On the opposite face the disk 37 is formed with an axial recess 44 which accommodates the fiap valve 32. The movement of the flap valve is limited by an annular plate 46 having openings 47 and which is seated in a groove 38 formed in the end of the clamping ring 38 and the adjacent face of the disk 37. It is to be noted that the flap valve 32 has an outer circumference which is disposed in line with the lower edge of the openings 47 in the annular plate 46. Also, the flap valve is formed with a chamfered surface 48 merging with a face 49 which is disposed in line with an annular passage 51 defined between the outer circumference of the piston rod 19 and the inner circumference of the opening in the annular plate 46.

The piston head assembly 17 may be formed of a forging or the like including the piston head 18 and the piston rod 19. The piston head 18 is of somewhat lesser diameter than the inner diameter of the cylinder so as to preclude metal-to-metal contact. Seated within a groove formed in the periphery of the piston head 18 is a piston ring which is preferably formed from a plastic or the like and not described in further detail.

The piston rod 19 passes through the intermediate cylinder head assembly 16, the stationary draft gear plate 20 and is threaded to the movable draft gear plate 21. In this connection it is to be observed that conventional resilient means are disposed between the stationary and movable plates 20 and 21 so as to yieldably resist impact on the coupler.

As heretofore described one end of the accumulator boot 22 is clamped to the intermediate cylinder head assembly 16. The other end of the boot is reversely turned inwardly and a beaded end thereof is clamped to the piston rod 19. The clamping arrangement includes a snap ring 56 seated in a groove formed in the piston rod 19 and retaining a clamping ring 57 in clamping relationship with a slidable clamping ring 58 which is held in position by a slidable sleeve 59 fixed against longitudinal movement by means of a second snap ring 61 seated in the piston rod. The flexible boot or accumulator is preferably formed of a laminated rubber so as to be expandable and to exert a pressure on the hydraulic fluid when the latter is introduced therein.

The fluid passageway 23 includes a passage 62 which communicates with passages 63 communicating with the accumulator boot 22. An enlarged bore 63 in the piston rod 19 and piston 17 communicates with the passage 62. The enlarged bore 63 also communicates with radially extending passages 64 best shown in FIG. 1 the same normally being closed by means of the slide valve assembly 29. The slide valve assembly 29 comprises a valve element 65 which is slidable on the outer peripheral surface of the piston rod 19. The piston 18 includes a plurality of small bores 66 communicating with opening 67 in turn communicating with the chamber 27. A piston element 68 is disposed in each of the bores 66 and is slidable therein. The piston elements 68 are suitably connected to the valve element 65 for moving the same to an open position relative to the passages 64 during predetermined pressure in the chamber 24.

The pressure relief valve assembly 28 comprises a valve plate element 69 held in position by means of a snap ring 70 against a shoulder 71 of the bore 63 The valve plate element 69 is provided with a restricted orifice 72 which is closed by means of a spherical member or ball 72 A frusto-conical valve member 73 is slidably positioned in the bore 63 The valve member 73 is provided with a eircumferentially conical front face 74 and a rear substantially flat face 75. A plurality of passages 76 extend from the front face 74 in oblique fashion relative to the axis of the valve member 73 and converge in a recessed area 77 on the rear flat face 75. A coil spring 78 includes a plurality of coils 79, one end of the spring 78 being supported by a shoulder 80 provided at the juncture of the passage 62 and the bore 63 The other end of the spring 78 is in biasing abutment with respect to the rear flat face thus normally maintaining the ball 72 in sealing engagement relative to the orifice 72. The coils 79 have an inner diameter which is greater than the converging area 77 and thus provide a clear passage for the fluid in the event the pressure within the chamber 24 exceeds a predetermined pressure whereupon the valve member 73 is moved to the open position. In this particular condition the pressure is immediately relieved since fluid freely flows through the clear passage provided by the inner diameter of the coils 79 of the spring 78 to thereby direct fluid through the passage system 23 and to the accumulator 22.

The operation In operation the cushion device 10 is disposed in a pocket adjacent the draft gear 11, with the base plate 14 engaged in suitable stops (not shown). Upon an application of an impact force in buff to a coupler, not shown, the plate 21 to which one end of the piston rod 19 is fixed moves inwardly so that the piston rod assembly 17 moves to the left from the neutral position shown in FIG. 1. The movement of the piston 18 to the left causes fluid to flow from the chamber 24 through the metering grooves 31 into the chamber 27 at the same time the pressure forces being exerted on the actuating pistons 68 of the slide valve assembly 29 are moved inwardly so that the slide ring 65 is displaced away from the ports 64 permitting fluid to flow from the chamber 27 through the ports 64 into the bore 63 through the passage 62, openings 63 into the accumulator boot 22. Thus, the fluid displaced by movement of the piston 18 through the chamber 24 is displaced into the accumulator boot 22.

During the operation in which the piston head 18 moves to the buff position against the plate 14, the flat valve 32 remains seated over the annular opening 33 providing communication between the chamber 27 and the accumulator boot 22, so that fluid flow only occurs through the passageway system 23 as above described. Such seating of the flat valve 32 occurs due to the pressure forces being exerted on the face 48.

When the buff impact has been dissipated and in the absence of a draft impact the return spring 34 disposed between the ledge 36 of the base plate 14 and the stationary plate is operative to return the unit to its neutral position shown in FIG. 1. In the event a draft impact is applied, the return spring 34 will assist in returning the piston head assembly 17 to the neutral position. During return movement the fluid pressure forces acting on the slide ring 65 of the slide valve assembly 29 are operative to return the actuating pistons 68 to a position preventing fluid flow through the openings 64. At the same time the hydraulic fluid flow is reversed from the chamber 27 to the chamber 24 via the metering grooves 31.

The metered flow of the fluid from the chamber 27 to 24 via the grooves 31 yields a predetermined force travel characteristic to achieve requisite lading protection. In view of the fact that the pressure forces in the chambers 24 and 27 are reversed from those occurring during buff impact, the flat valve 32 will remain in closed relationship over the annular opening 33 so that fluid does not enter the accumulator boot 22. When the piston head assembly 17 returns to its neutral position and is stationary, a pressure differential occurs between the accumulator boot 22 and chamber 27 so that fluid pressure forces in the boot 22 are operative to displace the flat valve 32 away from the opening permitting a return of the displaced hydraulic fluid so that the flat valve 32 is freely movable is to be noted that the chamfered surface 48 of the flat valve minimizes a reaction due to Bernoulli effect of the hydraulic fluid so that the flat valve 32 is freely movable when this unit is stationary.

Supposing now that the cushion unit through the coupler is subjected to an overspeed impact of a degree for which the unit is not specifically designed. At a predetermined pressure within the chamber 24 the pressure relief valve mechanism 28 is operative and assumes the position shown in FIG. 2. In this case fluid is released through the orifice 72 since the ball 72 is moved to the right. The valve element 73 has now been moved to compress the spring 78. Fluid now immediately surges through the openings 76 into the area of convergence 77 and directly through the opening provided by the enlarged inner diameter of the spring coils 79 through the passage 62 and into the boot 22. This arrangement provides for the immediate and effective release of a large quantity of liquid without any impediment interruption of the flow which might otherwise result in excessive pressure within the chamber 24 and thereby during overspeed impact cause destruction of or damage to the unit. By virtue of freedom of movement of the fluid through the pressure relief valve the objects of the invention are achieved.

It must be understood that changes and modifications in the preferred embodiment may be made which do not depart from the spirit of the invention.

What is claimed is:

1. In a cushion ..device adapted to relieve the buff and draft impacts-imposed on the couplers of a railway car, said cushion device including, a cylinder having a closed end and an open end, a piston assembly including a piston head and. piston rod positioned in said cylinder for relative sliding movement, a first chamber defined by said piston head and said closed end, an intermediate cylinder head mounted in said cylinder limiting said travel of said piston head assembly in one direction, an accumulator chamber on said cylinder including means closing the open end of said chamber, passageway means formed in said piston head assembly providing communication between said accumulator chamber and a second chamber defined by said piston head and said intermediate head, and metering means on said cylinder providing communication of fluid between said first and second chambers during movement of said piston assembly; a pressure relief valve arrangement comprising:

a passage extending longitudinally within said piston rod,

said passage including opening means in communication with said accumulator chamber,

a valve element including an orifice in said piston head, a longitudinal bore in said piston head concentric with said orifice and said passage,

a valve member slidably supported in said bore, said valve member having a front side facing said orifice and a rear side, biasing means in said bore engaging the rear side and moving said valve member into engagement with said orifice to normally close the same,

a plurality of passages in said valve member extending obliquely relative to the axis of said bore from the front side and converging at the rear side thereof in an area the size of which is defined by the combined inner diameters of said oblique passages,

said valve member being moved from closing engagement with said orifice during a predetermined pres sure in said first chamber whereby fluid passes therefrom through said oblique passages, said first passage, and opening means to said accumulator chamber,

a second opening means in said piston rod communicating with said passage and said second chamber,

a second valve member movably supported within said second chamber relative to said second opening for opening and closing the same,

a second longitudinal bore within said piston head opening outwardly into said first and second chambers, and

a piston element slidably disposed in said second bore and connected to said second valve member whereby during a pressure differential between said first and second chambers said piston element moves said second valve member to its open position and fluid passes from said second chamber through said second opening means to said passage.

References Cited UNITED STATES PATENTS 2,886,058 5/1959 Horton 137540 X 3,189,046 6/1965 Callahan et al. 137540 X 3,275,164 9/1966 Peterson 213-43 FOREIGN PATENTS 1,123,507 6/1956 France.

GEORGE E. A. HALVOSA, Primary Examiner US. Cl. X.R. 

